I am able to drill out the head and it pops off and stays stuck on the drill bit, works like a charm. But ever with a 7/32" bit, the shank of the rivet down in the bottom of the hole i.e. on the lower sheet stays in the hole. I guess the rivet shank gets expanded and is too big a dia for the drill. I end up trying to get a sharp punch in there to grab an edge and fold it inwards, then I can punch it out. A pain in the butt. But doable. The fact that these rivets are strong makes them hard to remove, which I suppose is a good thing in a way. Thanks for all the replies.